This method is for determining moisture in gas or liquid hydrocarbon streams with the use of an on-line analyzer. The method is primarily a summary of available instruments that can be selected. The instrument and sampling system associated with a UOP process unit is specified by UOP depending on the process unit and analysis requirements. The actual procedure to be followed is dependent on the specific instrument and vendor chosen. Moisture concentrations in the range of a few tenths of a ppm to percent (mole or volume) can be determined.